Bundoora, Australia
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Powell K.J.,University of Canterbury | Brown P.L.,Research Avenue | Byrne R.H.,University of South Florida | Gajda T.,University of Szeged | And 4 more authors.
Pure and Applied Chemistry | Year: 2013

The numerical modeling of ZnII speciation amongst the environmental inorganic ligands Cl-, OH-, CO32-, SO42-, and PO43-requires reliable values for the relevant stability (formation) constants. This paper compiles and provides a critical review of these constants and related thermodynamic data. It recommends values of log10βp,q,r° valid at Im = 0 mol·kg-1 and 25 °C (298.15 K), and reports the empirical reaction ion interaction coefficients, Δ∈required to calculate log10βp,q,r values at higher ionic strengths using the Brønsted-Guggenheim-Scatchard specific ion interaction theory (SIT). Values for the corresponding reaction enthalpies, ΔrH, are reported where available. There is scope for additional high-quality measurements for the Zn2+ + H+ + CO32-system and for the Zn2+ + OH-and Zn2+ + SO42-systems at I > 0. In acidic and weakly alkaline fresh water systems (pH <8), in the absence of organic ligands (e.g., humic substances), ZnII speciation is dominated by Zn2+(aq). In this respect, ZnII contrasts with CuII and PbII (the subjects of earlier reviews in this series) for which carbonato-and hydroxido-complex formation become important at pH > 7. The speciation of ZnII is dominated by ZnCO3(aq) only at pH > 8.4. In seawater systems, the speciation at pH = 8.2 is dominated by Zn2+(aq) with ZnCl+, Zn(Cl)2(aq), ZnCO3(aq), and ZnSO4(aq) as minor species. This behaviour contrasts with that for CuII and PbII for which at the pH of seawater in equilibrium with the atmosphere at 25 °C (log10 {[H+]/c°} ≈ 8.2) the MCO3(aq) complex dominates over the MCln(2-n)+ species. The lower stability of the different complexes of ZnII compared with those of CuII, PbII, and CdII is also illustrated by the percentage of uncomplexed M2+ in seawater, which is ca. 55, 3, 2, and 3.3% of [MII]T, respectively. © 2013 IUPAC.

Trenfield M.A.,Environmental Research Institute of the Supervising Scientist | Trenfield M.A.,University of Queensland | McDonald S.,Curtin University Australia | Kovacs K.,University of Szeged | And 7 more authors.
Environmental Science and Technology | Year: 2011

Fulvic acid (FA) from a tropical Australian billabong (lagoon) was isolated with XAD-8 resin and characterized using size exclusion chromatography, solid state cross-polarization magic angle spinning, 13C nuclear magnetic resonance spectroscopy, elemental analysis, and potentiometric acid-base titration. Physicochemical characteristics of the billabong FA were comparable with those of the Suwannee River Fulvic Acid (SRFA) standard. The greater negative charge density of the billabong FA suggested it contained protons that were more weakly bound than those of SRFA, with the potential for billabong water to complex less metal contaminants, such as uranium (U). This may subsequently influence the toxicity of metal contaminants to resident freshwater organisms. The complexation of U with dissolved organic carbon (DOC) (10 mg L-1) in billabong water was calculated using the HARPHRQ geochemical speciation model and also measured using flow field-flow fractionation combined with inductively coupled plasma mass-spectroscopy. Agreement between both methods was very good (within 4% as U-DOC). The results suggest that in billabong water at pH 6.0, containing an average DOC of 10 mg L-1 and a U concentration of 90 μg L-1, around 10% of U is complexed with DOC. © 2011 American Chemical Society.

Drieberg S.L.,University of Western Australia | Hagemann S.G.,University of Western Australia | Huston D.L.,Geoscience Australia | Landis G.,U.S. Geological Survey | And 4 more authors.
Economic Geology | Year: 2013

The ∼3240 Ma Panorama volcanic-hosted massive sulfide (VHMS) district is unusual for its high degree of exposure and low degree of postdepositional modification. In addition to typical seafloor VHMS deposits, this district contains greisen- and vein-hosted Mo-Cu-Zn-Sn mineral occurrences that are contemporaneous with VHMS orebodies and are hosted by the Strelley granite complex, which also drove VHMS circulation. Hence the Panorama district is a natural laboratory to investigate the role of magmatic-hydrothermal fluids in VHMS hydrothermal systems. Regional and proximal high-temperature alteration zones in volcanic rocks underlying the VHMS deposits are dominated by chlorite-quartz ± albite assemblages, with lesser low-temperature sericite-quartz ± K-feldspar assemblages. These assemblages are typical of VHMS hydrothermal systems. In contrast, the alteration assemblages associated with granite-hosted greisens and veins include quartz-topaz-muscovite-fluorite and quartz-muscovite (sericite)-chlorite-ankerite. These vein systems generally do not extend into the overlying volcanic pile. Fluid inclusion and stable isotope studies suggest that the greisens were produced by high-temperature (∼590°C), high-salinity (38-56 wt % NaCl equiv) fluids with high densities (>1.3 g/cm3) and high δ18O (9.3 ± 0.6‰). These fluids are compatible with the measured characteristics of magmatic fluids evolved from the Strelley granite complex. In contrast, fluids in the volcanic pile (including the VHMS ore-forming fluids) were of lower temperature (90°-270°C), lower salinity (5.0-11.2 wt % NaCl equiv), with lower densities (0.88-1.01 g/cm3) and lower δ18O (-0.8 ± 2.6‰). These fluids are compatible with evolved Paleoarchean seawater. Fluids that formed the quartz-chalcopyrite- sphalerite-cassiterite veins, which are present within the granite complex near the contact with the volcanic pile, were intermediate in temperature and isotopic composition between the greisen and volcanic pile fluids (T = 240°-315°C; δ18O = 4.3 ± 1.5‰) and are interpreted to indicate mixing between the two end-member fluids. Evidence of mixing between evolved seawater and magmatic-hydrothermal fluid within the granite complex, together with the lack of evidence for a magmatic component in fluids from the volcanic pile, suggest partitioning of magmatic-hydrothermal from evolved seawater hydrothermal systems in the Panorama VHMS system. This separation is interpreted to result from either the swamping of a relatively small magmatic-hydrothermal system by evolved seawater or density contrasts precluding movement of magmatic-hydrothermal fluids into the volcanic pile. Variability in the salinity of fluids in the volcanic pile, combined with evidence for mixing of low- and high-salinity fluids in the massive sulfide lens, is interpreted to indicate that phase separation occurred within the Panorama hydrothermal system. Although we consider this phase separation to have most likely occurred at depth within the system, as has been documented in modern VHMS systems, the data do not allow the location of the inferred phase separation to be determined. © 2013 Society of Economic Geologists, Inc.

Powell K.J.,University of Canterbury | Brown P.L.,Research Avenue | Byrne R.H.,University of South Florida | Gajda T.,University of Szeged | And 4 more authors.
Pure and Applied Chemistry | Year: 2011

The numerical modeling of CdII speciation amongst the environmental inorganic ligands Cl-, OH-, CO3 2-, SO4 2-, and PO4 3- requires reliable values for the relevant stability (formation) constants. This paper compiles and provides a critical review of these constants and related thermodynamic data. It recommends values of log10 βp,q,r° valid at Im = 0 mol kg-1 and 25 °C (298.15 K), along with the equations and empirical reaction ion interaction coefficients, Δε, required to calculate log10 βp,q,r values at higher ionic strengths using the Brønsted-Guggenheim-Scatchard specific ion interaction theory (SIT). Values for the corresponding reaction enthalpies, ΔrH, are reported where available. Unfortunately, with the exception of the CdII-chlorido system and (at low ionic strengths) the CdII-sulfato system, the equilibrium reactions for the title systems are relatively poorly characterized. © 2011 IUPAC.

Costine A.,CSIRO | Nikoloski A.N.,Murdoch University | Costa M.D.,CSIRO | Chong K.F.,Murdoch University | And 2 more authors.
Minerals Engineering | Year: 2013

Brannerite is a refractory uranium mineral from which it is very difficult to liberate the uranium. Hence in commercial mineral processing operations, brannerite often reports to the residue. This paper will show that for a pure form of natural brannerite nearly complete extraction of uranium (∼99%) is achievable under practical conditions. The efficient extraction of uranium from ores containing brannerite requires a detailed understanding of the fundamental mechanisms governing the rate and extent of dissolution. These mechanisms are often complicated by the presence of gangue minerals which consume reagents and impact on the solution chemistry. In this study, the acidic ferric sulphate leaching of an exceptionally pure, natural brannerite mineral (35.8% U, 20.1% Ti) was investigated under atmospheric conditions. Hence the variation in mineral composition was not present as a complicating factor and the results were able to identify some of the inhibiting mechanisms, and also the preferred conditions for the leaching of brannerite in an acidic ferric sulphate system. The effects of temperature (40-80 C), ferric ion concentration (0-100 g/L), H2SO4 concentration (10-200 g/L), redox potential (424-752 mV vs. Ag/AgCl), and particle size on uranium and titanium extractions were studied for leach times up to 48 h. Under relatively mild conditions (40 C, 24 h leach time, 40 g/L H2SO4), the extent of uranium extraction was 94.4%. The extractions improved with the use of a higher temperature, a finer particle size, and a longer leach time. The presence of ferric iron was essential for enhanced dissolution rates, but had only a minor effect on the final uranium extractions, particularly at 60 C and 80 C. All of the leach residues studied had some crystalline anatase (TiO2) and lead sulphate (anglesite) present. A strong correlation was found between the concentrations of unleached uranium and the amount of titanium precipitated in the residues, which could be explained by the observation of a Ti-enriched diffusion layer on the surface of the dissolving grains of brannerite, which hindered the extraction process. These findings further the current understanding of the extraction process and lead a step closer to elucidation of the mechanism of the extraction process. © 2013 Elsevier B.V. All rights reserved.

Cao G.,Level Inc | Zhang X.,Research Avenue | Zhang H.,Level Inc
TMS Light Metals | Year: 2014

The importance of the cathode assembly thermal-electrical and thermal-mechanical performance cannot be overstated when designing an aluminum reduction cell. However, it is extremely difficult to measure in-service cathode assembly performance or to infer in-service behaviour from any measurements of cathode assemblies at room temperature. A complete thermo-electrical and thermo-mechanical modelling approach has been developed to conduct sequentially coupled simulation of the cathode assembly lifecycle performance. The modelling starts with the cathode rodding process which allows the air gap between the cast iron and carbon to be predicted. The results are built into the subsequent thermo-electrical and thermo-mechanical models of the in cell operation. The cathode voltage drop is then estimated by coupling the predicted contact pressure and temperature with the electrical contact resistance. The model predicted air gaps as well as cathode voltage drop savings due to design changes have been validated by carefully designed experimental measurements for various cathode assembly designs. Copyright © 2014 by The Minerals, Metals & Materials Society.

Bhargava S.K.,RMIT University | Ram R.,RMIT University | Pownceby M.,CSIRO | Grocott S.,Research Avenue | And 3 more authors.
Hydrometallurgy | Year: 2015

Uraninite is mined/processed more than any other uranium mineral for the production of uranium based compounds that are subsequently used to produce nuclear fuel. This review article provides a concise account of the available literature on one of the major processes involved in processing uraninite bearing ores, acid leaching. Improvements in the processes used to leach uraninite are required in order to ensure efficiency in the processing of lower grade uraninite bearing ores with minimal environmental impacts. This in turn requires improvements in our understanding of uraninite leaching. The main topics covered in this review include: uraninite structure, composition and low temperature geochemistry; the chemistry of uraninite leaching; key factors that influence uraninite leaching; and leach process technologies. The research that has been reviewed clearly establishes the influence of parameters such as temperature, acid concentration and particle size. The influence of other parameters however, such as solution Fe3 + to Fe2 + ratio (solution Eh), total Fe concentration, foreign ions present in the leach slurry and uraninite composition is yet to be established. Based on the literature available on the aforementioned factors the chemistry/processes involved in uraninite leaching are quite complex and require significant further studies. From the literature reviewed it is clear that variations in mineral chemistry in individual ore types across multiple deposits also make it essential that before any extraction process is considered, detailed ore characterisation studies of pre- and post-leach residues are of vital importance in order to fully understand the interrelationship between chemistry, mineralogy (ore and gangue), mineral liberation and potential leaching behaviour of uranium. © 2014 Elsevier B.V.

Kaksonen A.H.,CSIRO | Mudunuru B.M.,CSIRO | Hackl R.,CSIRO | Hackl R.,Research Avenue
Hydrometallurgy | Year: 2014

With a projected steady decline of gold ore grade in mineral resources, mining applications enabling efficient metal extraction from low-grade ores are of increasing interest to the minerals industry. Microbial processes may provide one such solution since they can participate in the biogeochemical cycling of gold in many direct and indirect ways. This review examines current literature on the role of microorganisms in gold processing and recovery. The review covers aspects such as the biotechnical pre-treatment of gold ores and concentrates, microbially catalysed permeability enhancement of ore bodies, gold solubilisation through biooxidation and complexation with biogenic lixiviants, and microbially mediated gold recovery and loss from leach liquors. © 2013 Elsevier B.V.

Cheng C.Y.,CSIRO | Boddy G.,Research Avenue | Zhang W.,CSIRO | Godfrey M.,Research Avenue | And 5 more authors.
Hydrometallurgy | Year: 2010

In Part 1 of this paper, two synergistic solvent extraction systems consisting of Versatic 10/LIX63/TBP and Versatic 10/4PC were assessed in batch tests for the separation and purification of nickel and cobalt from synthetic laterite leach solution after iron removal. In Part 2, semi- and fully-continuous tests are reported for the Versatic 10/LIX63/TBP system, with conditions optimised for separating nickel and cobalt from manganese, magnesium and calcium. Semi-continuous extraction tests were conducted using the synergistic organic system consisting of 0.50 M Versatic 10, 0.45 M LIX63 and 1.0 M TBP in Shellsol D70. With a pH profile of 5.5/6.1/6.5 for the three stages EX1/EX2/EX3 at 40 °C, the nickel and cobalt extractions were 99.9% with only 5 mg/L nickel and < 1 mg/L cobalt left in the raffinate. With two stages of scrubbing and a pH profile of 5.4/5.0 at 40 °C, about 2 mg/L manganese and less than 1 mg/L magnesium and calcium were left in the scrubbed organic solution. With two stripping stages and an O/A ratio of 10 at 40 °C using 50 g/L H2SO4 as strip solution, the stripping efficiencies of nickel and cobalt were over 95%. A fully-continuous pilot plant was operated for 280 h. With an O/A ratio of about 2 and a pH profile of 5.5/5.8/6.0/6.3 for the four stages EX1/EX2/EX3/EX4 at 40 °C, both nickel and cobalt were almost completely extracted. The nickel and cobalt concentration in the raffinate was lower than detection limit of 0.2 mg/L. The manganese, magnesium and calcium concentrations in the loaded organic solution were 34, 8 and 1 mg/L, respectively. Using a pH profile of 5.4/5.0 for SC1/SC2 at an O/A ratio of 10 and 40 °C, the manganese scrubbing efficiency was over 96% and the concentrations of manganese and magnesium in the scrubbed organic solution were < 5 mg/L and that of calcium 1 mg/L. Using three strip stages and a strip solution containing 50 g/L H2SO4 and 55 g/L Ni at an O/A ratio of 10 and 40 °C, over 98% Ni and 99% Co were stripped with only 64 mg/L Ni in the stripped organic solution. The nickel concentration in the loaded strip liquor was 86 g/L, giving a ΔNi of 31 g/L. The loaded strip liquor contained less than 1 g/L acid. © 2010 Elsevier B.V.

Cheng C.Y.,CSIRO | Boddy G.,Research Avenue | Zhang W.,CSIRO | Godfrey M.,Research Avenue | And 4 more authors.
Hydrometallurgy | Year: 2010

The separation of nickel and cobalt from impurities such as manganese, magnesium and calcium using solvent extraction with Versatic 10 was largely improved by the addition of a synergistic reagent LIX63 (an α- hydroxyoxime) or 4PC (a pyridine carboxylate ester). With the organic systems containing Versatic 10 alone, the separation factors of nickel and cobalt over manganese were 6 and 15 respectively. When 4PC was added to the system, these increased to 147 and 1870 respectively, and with LIX63, they were even higher at 534 and 7720 respectively. This indicates that the synergistic solvent extraction (SSX) system with Versatic 10 and LIX63 performed very well and better than that with Versatic 10 and 4PC. The SSX system consisting of 0.5 M Versatic 10, 0.45 M LIX63 and 1.0 M TBP in Shellsol D70 performed the best among the systems tested containing LIX63. After a single contact, the extraction of Ni and Co was 99.6% and 96.9%, respectively. Only 6 mg/L Mn, 8 mg/L Mg and 1 mg/L Ca were found in the loaded organic solution. The manganese scrub efficiency was 97.7% at pH 5.3, resulting in a scrubbed organic solution containing only 0.8 mg/L Mn. Over 99% nickel, cobalt and manganese were stripped at pH 2.0, indicating easy stripping of these metals. The SSX system consisting of 0.5 M Versatic 10 and 1.0 M 4PC in Shellsol D70 performed the best among the systems tested containing 4PC. After a single contact, the extraction of Ni and Co was 99.4% and 89.4%, respectively. Some 200 mg/L Mn, 10 mg/L Mg and 48 mg/L Ca were found in the loaded organic solution. The manganese could not be scrubbed at the tested pH range of 5.4-6.0. Very fast Ni and fast Co stripping kinetics were observed, however, the Mn stripping kinetics were very slow. After 2 min of stripping, only 1.22% Mn was stripped. It is concluded that the SSX system containing 0.5 M Versatic 10, 0.45 M LIX63 and 1.0 M TBP performed much better than the SSX system containing 0.5 M Versatic 10 and 1.0 M 4PC in terms of both manganese and calcium behaviour in extraction, scrubbing and stripping. © 2010 Elsevier B.V.

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